The present invention relates to a disk drive for use in recording and reproducing data on a disk-shaped recording medium such as a magnetic disk and, in particular, to a carriage mechanism of the disk drive.
Referring to FIGS. 1 through 3, a conventional magnetic disk drive designed for magnetic disks will be described. Such a magnetic disk drive is disclosed in, for example, Japanese Patent Laid-Open (JP-A) No. 9-91943. In the magnetic disk drive illustrated in FIG. 1, a reception mechanism and an ejection mechanism for receiving and ejecting a magnetic disk, respectively, are omitted for clarity of illustration. A chassis 10 comprises a pair of side walls 10-1 on both sides thereof. All components and parts are mounted on a principal surface of the chassis 10. A main printed wiring board 11 and a subsidiary printed wiring board 20 are fixed by screws to the principal surface of the chassis 10. For the main printed wiring board 11, two support members 10-2 (FIG. 2) are formed integrally with the chassis 10 by cutting and rising corresponding portions of a principal plate of the chassis 10. The main printed wiring board 10 is fixed onto the support members 10-2 by the use of screws 12.
A stepping motor 13 is attached to a rear wall 10-3 at a rear end of the chassis 10. An output shaft 13-1 of the stepping motor 13 penetrates through the rear wall 10-3. The output shaft 13-1 has a top end rotatably supported by a shaft receptacle 10-4 integrally formed with the chassis 10 by cutting and rising a corresponding portion of the principal plate of the chassis 10. The output shaft 13-1 has a threaded outer peripheral surface. A carriage mechanism 14 is provided with an arm 14-1 with a pin 14-2 embedded therein. The pin 14-2 is engaged with the threaded outer surface of the output shaft 13-1. With this structure, rotation of the output shaft 13-1 brings about the movement of the carriage mechanism 14 in the same direction as the output shaft 13-1. On the carriage mechanism 14, magnetic heads are mounted for access to the magnetic disk. The carriage mechanism 14 serves to move the magnetic heads in the radial direction of the magnetic disk.
The carriage mechanism 14 is provided with a U-shaped bearing arm 14-3 formed on the side opposite to the arm 14-1. A guide bar 15 penetrates through the bearing arm 14-3. The guide bar 15 is held by a guide bar clamp 16. With this structure, the carriage mechanism 14 is guided by the guide bar 15 during the movement following the rotation of the output shaft 13-1. The guide bar clamp 16 is fixed by a screw to a support plate 10-5 (FIG. 2). The support plate 10-5 is formed integrally with the chassis 10 by cutting and rising a corresponding portion of the principal plate of the chassis 10, and projects upward through a hole formed in the main printed wiring board 11.
In FIG. 3, a motor 21 for rotating the magnetic disk and other circuit components (not shown) are mounted on a subsidiary printed wiring board 20 only on the upper surface thereof. Accordingly, the subsidiary printed wiring board 20 is fixed to the principal plate of the chassis 10 by the screws 12 (FIG. 1) to be substantially in contact therewith at the position closer to a slot for the magnetic disk, i.e., to a front bezel 17.
The structure of the motor 21 will briefly be described. The motor 21 comprises a rotation shaft 21-1, a center metal 21-2, a plurality of cores 21-3, a plurality of stator coils 21-4, a ring-shaped permanent magnet 21-5, and a circular casing 21-6 attached to the rotation shaft 21-1. The center metal 21-2 has a cylindrical shape and serves as a bearing. Each of the cores 21-3 radially outwardly extends from the center. Each of the stator coils 21-4 is wound around an end portion of each corresponding core 21-3. The permanent magnet 21-5 surrounds these cores 21-3. The casing 21-6 holds the permanent magnet 21-5. When the rotation shaft 21-1 is rotated, the permanent magnet 21-5 and the casing 21-6 rotate together with the rotation shaft 21-1. A reference numeral 21-7 depicts an index magnet. A combination of the cores 21-3 and the stator coils 21-4 serves as a stator of the motor 21. A combination of the permanent magnet 21-5 and the casing 21-6 serves as a rotor of the motor 21. The stator and the rotor of the type are disclosed in, for example, Japanese Patent Laid-Open (JP-A) No. 9-91866 and, therefore, will not be described herein in detail.
Referring to FIGS. 4 and 5, a core assembly is formed by a plurality of stator cores 21-3 radially outwardly extending from an outer periphery of a ring-shaped member 21-3L (FIG. 4) of metal. The ring-shaped member 21-3L has an inner diameter greater than the outer diameter of the center metal 21-2 (FIG. 5). The ring-shaped member 21-3L is provided with a pair of attaching elements 21-3a formed on its inner periphery at positions opposite to each other and extending towards the center metal 21-2 (FIG. 5). Each of the attaching elements 21-3a has an end provided with an arc-shaped portion having the diameter substantially equal to the outer diameter of the center metal 21-2.
Referring back to FIG. 3, the casing 21-6 has a protruding portion formed at its center and a flat portion 21-6a formed on an upper surface of the protruding portion. To the flat portion 21-6a, a disk table 21-8 formed by a plastic magnet is integrally fixed. The flat portion 21-6a is provided with an arm 22 attached to a bottom surface thereof. A drive roller 23 is rotatably mounted on the arm 22. Each of the flat portion 21-6a and the disk table 21-8 has a generally rectangular hole formed therein. Through these holes, the drive roller 23 projects upward from the disk table 21-8. The magnetic disk received in the magnetic disk drive is placed on the disk table 21-8. The drive roller 23 is inserted in and engaged with a hole formed in a hub of the magnetic disk. Thus, the magnetic disk is rotated following the rotation of the rotor. The disk table 21-8 is disclosed in, for example, Japanese Patent Laid-Open (JP-A) No. 9-91814 and is not described in detail herein.
Above the motor 21, an eject plate 24 and a disk holder unit 25 are incorporated as the ejection mechanism the reception mechanism for the magnetic disk, respectively. The eject plate 24 and the disk holder unit 25 are also disclosed in the above-mentioned Japanese Patent Laid-Open (JP-A) No. 9-91814 or 9-91943. The chassis 10 is coupled with a cover plate 18 to protect an internal space inside the chassis 10.
Next referring to FIG. 5, assembling of the stator will be described. The center metal 21-2 has a flange portion 21-2a formed at its lower part. The chassis 10 is provided with an opening 10-9 having the size corresponding to the cylindrical portion of the center metal 21-2. The subsidiary printed wiring board 20 is provided with an opening having the size corresponding to the flange portion 21-2a. Each of the attaching elements 21-3a of the core assembly and the subsidiary printed wiring board 20 is provided with a pair of holes for receiving screws 31 inserted therethrough while the chassis 10 is provided with threaded holes to be engaged with the screws 31.
The assembling is carried out as follows. At first, the lower part of the center metal 21-2 is inserted into the opening 10-9 of the chassis 10 and is caulked at the edge of the opening 10-9 to tightly fix the center metal 21-2 to the chassis 10. Then, the subsidiary printed wiring board 20 is placed on the chassis 10 and positioned so that the center of the opening of the subsidiary printed wiring board 20 coincides with the center of the center metal 21-2. In this state, the attaching elements 21-3a of the core assembly are stacked with a ring-shaped spacer 30 interposed therebetween. Then, the chassis 10, the subsidiary printed wiring board 20, and the core assembly are integrally assembled by the screws 31. The spacer 30 also serves to position the core assembly in a vertical direction. Since the center metal 21-2 is fixed by caulking at its lower part as described above, the conventional stator requires a long assembling time. Also, it takes a long time to position the subsidiary printed wiring board 20 and the core assembly with respect to the center of the center metal 21-2.